In the design and development of machine parts, it is often desirable to prepare a prototype of a newly created part. This allows the manufacturer to ensure that the new part will properly integrate with the other parts with which it interacts, or conversely allows changes to be incorporated into the part design if problems arise, prior to the creation of expensive commercial production tooling. As the design and development of parts can often become a trial-and-error process, the ability to quickly and accurately prepare prototypes is very desirable. Further, prototypes that are created should possess sufficient strength to withstand chipping, cracking, and other structural problems that may arise during testing of the part with other components, and even during normal handling of the part.
Various methods which provide for the preparation of such prototypes and, more generally, of three-dimensional bodies of a predetermined size and shape, are known in the art. Several of these methods involve the controlled, sequential deposition of layers of material upon one another.
One method of forming three-dimensional bodies by such a method is stereolithography. A description of stereolithography can be found in U.S. Pat. No. 4,575,330. In this patent, a low viscosity bath of a particular photopolymerizable homogenous monomer solution is prepared. A platform, which moves relative to the surface of the solution, is located in the solution. Upon operation, the platform is lowered until it resides slightly below the surface of the solution. A movable laser, which is mounted onto a CAD-CAM controlled head, is located over the solution. The laser is selected so that, when it is activated and moved with respect to the platform, a polymer layer is created from the homogenous monomer solution. In other words, the monomer polymerizes locally when the light emitted by the laser reaches the monomer solution. The platform is then lowered until it is slightly below the surface of the solution, so that the low viscosity homogenous monomer solution flows over the photopolymerized layer. The process is then repeated until a plurality of layers, and therefore the desired three-dimensional body, is formed.
Such systems are limited, however, in that only photopolymerizable liquids can be used. This further requires the use of a laser to effect polymerization, making the apparatus used to conduct this method relatively expensive. Moreover, as a practical matter, only a single liquid composition is able to be used to prepare a body. In addition, it would be difficult to prepare a ceramic prototype part using this method because it would be difficult to achieve adequate dispersion of such particles throughout the liquid and, even if this problem were overcome, the ceramic particles would scatter the impinging laser beam. Further, the successive layers may only be formed in a single, horizontal plane.
Another method for the preparation of three-dimensional bodies which addresses some of the aforementioned deficiencies is described by U.S. Pat. No. 5,121,329. This method utilizes a spool fed filament, e.g., wax, a thermoplastic resin, or a metal, through a heated, fine diameter, nozzle. As the material passes through the nozzle, it melts. The nozzle, and therefore the molten material, is then moved relative to a surface so a layer of the material is deposited onto the surface in a predetermined pattern. The material is selected so that it solidifies when it contacts the relatively cool surface. Deposition of the material is repeated a number of times until a desired three-dimensional object, comprised of a number of such layers (one upon the other), is prepared.
This system, however, is limited as to the types of materials that can be used to form the body. More specifically, "meltable" materials are required to be used, such as thermoplastic resins, metals, waxes, and the like. Further, parts prepared using those materials and methodology typically exhibit poor mechanical properties, requiring careful handling to avoid damage. In addition, it is difficult to prepare parts having particulate loading because the melt viscosity of the material increases significantly with filler content. Another problem is that parts prepared using this method will generally further exhibit a certain degree of warpage.
In view of the foregoing limitations of known methods for providing three-dimensional bodies, e.g., prototype machine parts, of varying shapes, one object of the present invention is to provide a composition and method which allow the preparation of three-dimensional green bodies of varying shapes.
A further object of the present invention is to provide a composition and method for preparing three-dimensional bodies which, regardless of their shape, exhibit enhanced physical properties as compared to bodies of the same shape prepared using conventional compositions and methods.
Another object of the present invention is to provide a composition and method which allow the preparation of three-dimensional bodies of varying shapes using a relatively wider range of materials as the primary body component as compared to materials used in conventional compositions and methods.
Yet another object of the present invention is to provide a composition and method for the preparation of three-dimensional bodies which bodies possess a relatively lower level of warpage as compared to bodies prepared using known methods.
An additional object of the present invention is to provide a method which allows for the preparation of three-dimensional bodies having relatively high levels of particulate loading while avoiding the problems associated with such loading using prior art compositions and methods.
Another object of the present invention is to provide a method which provides a means for the preparation of a three-dimensional body which possesses predetermined specific, and different, mechanical properties in one area of the body as compared to a different area of the same body.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.